WASHINGTON — Twenty-three months after then-President Barack Obama declared a federal emergency over lead contamination in the Flint water supply, the U.S. Environmental Protection Agency is seeking input from states on changes to federal rules regarding how local water systems must react in similar situations.

On Thursday, an EPA director sent a letter to state environmental and other agencies that often oversee implementation of the federal Lead and Copper Rule, calling them to a meeting in Washington on Jan. 8 to discuss potential changes.

"Despite lead contaminated sites being an environmental threat to our country, EPA has not updated the Lead and Copper Rule in decades," said EPA Administrator Scott Pruitt, noting that no major revision has been made since its implementation in 1991.

While no level of lead is considered safe, the existing rule generally requires water systems to do periodic sampling of drinking supplies in consumers homes and forces them to take certain actions — such as treating or replacing lead service lines — if samples reach more than 15 parts per billion.

The existing rule has come under criticism, however, for relying too heavily on water systems to police themselves and on states to oversee the water samples those local systems submit for testing.

Since lead levels can be influenced by the quality and conditions of pipes in an individual home, as well as those leading to it, and other factors, such as construction in the area, it's not always clear the sites most at risk for lead contamination are even being tested.

In December 2015, amid the growing problem in Flint, an EPA working group issued recommendations that led the agency to begin looking at altering the rule to implement more aggressive lead water line replacement programs; improve public education campaigns to get consumers to test their water, and possibly set a "health-based benchmark" for lead that would, when exceeded in an individual's home, require notification of the individual and local public health agencies, with the expectation that officials would "use this information to take prompt action."

Flint's drinking water became contaminated with lead after it changed water sources to the Flint River and the state Department of Environmental Quality failed to require corrosion control treatments to keep lead from leaching out of old pipes into consumers' taps. While eventually residents were urged not to drink the unfiltered water, that notice came only after months from the state and the EPA.

While the letter Thursday to state officials invites them to the meeting in Washington, it also gives them 60 days thereafter to provide written input, meaning the final proposed rule is not expected for some time.

Contact Todd Spangler at 703-854-8947 or at tspangler@freepress.com. Follow him on Twitter at @tsspangler.